Field of the Invention
The present invention relates to wireline logging and, more particularly, in one or more embodiments, the present invention relates to a device for improving the conveyance of wireline logging tools down irregular and/or deviated boreholes while also acquiring data about the borehole environment.
Background of the Invention
Wireline logging is a common operation in the oil industry whereby down-hole electrical tools are conveyed on wireline (also known as “e-line” in industry parlance) to evaluate formation lithologies and fluid types in a variety of boreholes. In irregular shaped boreholes, characterized by variations in hole size with depth, and/or in deviated boreholes, there may be problems in conveying wireline logging tools to total well depth, since the bottom of the tool-string may impact upon certain features in the borehole such as ledges, washouts, or contractions. Additionally, high drags, mud properties, or accumulation of solids/debris may also result in early termination of the wireline descent. In this situation, full data acquisition from total well depth may not be possible and remedial action may be required, either altering the borehole conditions for more favorable descent or improving the tool-string configuration to navigate past the obstructions; either solution may be costly to the well operator.
The term “hole finder” is commonly used in the wireline industry for a device that connects below a logging tool-string to improve conveyance performance and to overcome obstacles in the borehole. Conventional hole finders do not contain independent sensing packages that are capable of acquiring data about the borehole environment.
The examination of mud properties at borehole depth intervals may provide important clues as to the root cause of the wireline descent problems. For example, formation fluid influxes may upset the rheology of the mud, resulting in a gelling which may obstruct the passage of the wireline logging tool-string down hole. The settling of drilling mud in deviated sections of the borehole may reduce the local buoyant tool-string weight and also increase the fluid drag force; both of which may negatively impact the tool-string descent down-hole. Conventional conveyance models, also known as wireline tension models, do not consider variable mud properties in their design, and assume that buoyancy and fluid forces remain constant from the borehole surface to total depth. The absence of the consideration of variable fluid properties in the modeling may lead to false assumptions about conveyance performance and consequently lead the wireline operator into serious operational difficulties.
Consequently, there is a need for improving wireline tool-string configuration to aid conveyance past ledges, washouts, and contractions which may be present in irregular shaped and/or deviated boreholes and to sense and understand the borehole environment to best estimate how the mud properties might impact the conveyance of wireline logging tools.